Fertilizers, Pesticides & IPM Review Notes
Fertilizers: Used to replace lost organic matter/nutrients in soil.
Organic / Inorganic (Synthetic)Organic matter from plants/animals.
Typically made from animal manure that has been allowed to decompose.
Nutrient availability dependent on decomposing rate / Produced commercially, highly concentrated
Fast acting, short lasting
Soluble & mobile (easily leach pollute)
Controlling Pests with Pesticides – estimated 1/3 of the potential harvest and 1/10 of the harvested crop are lost to pest
□Farms are in the early stages of ecological succession (+fertilizers and water) Good place for weeds (competition with crops for resources)
□Pesticide: substance that kills/controls the pest population (insecticides = insects, herbicides = plants/weeds)
- 1st generation: natural chemicals from plants
- 2nd generation: synthetic, created specifically for a pest
- Broad spectrum: Designed to kill many different types of pests
- Selective: Designed to kill a narrower range of organisms
□Persistence: Length of time they remain deadly in the environment for years, magnified in food webs (biomagnification)
□Bioaccumulation: Pesticides found built up over time in fatty tissue of predators (things that eat the insects/weeds sprayed with pesticides) Can lead to high pesticide concentrations in the higher tropic levels (biomagnification)
□Resistance: pest populations evolve resistance over time
- Pesticide treadmill: Cycle of pesticide development followed by pest resistance, followed by development of new pesticide (positive feedback loop!)
History of Pesticides
Pre-Industrial Revolution: slash & burn agriculture, planting aromatic herbs to repel insects
Modern science-based agriculture: looked for chemicals that would reduce the abundance of pests (original ones, like arsenic, killed everything)
Developed artificial organic compounds like DDT (broad spectrum) some compounds like Aldrin (used to control termites) found in human breastmilk
Return to biological/ecological knowledge
- Biological control: Use of natural predators/parasites to control pests proven safe and effective!
Integrated Pest Management
- Uses a variety of methods: biological control, chemical pesticides (limited use), crop planting methods (no-till/low till to build levels of natural pest enemies, crop rotation, intercropping, pest resistant crop varieties, creating habitats for predators)
- Goal: Control, but never complete elimination of pests. More cost effective and also does less damage to the ecosystem, soil, water, air.
- World pesticide use exceeds 2.5 billion kg. (US > 680 million kg)
- $32 billion worldwide, $11 billion in US
- Once applied can decompose in place (takes a long time) or be carried by wind/water
- Breakdown products can be toxic